Combustion of petroleum diesel fuel is a major source of fine (d 2.5 m) and ultrafine (d 0.1 m) particulate matter (PM) in the environment, with substantial impact on cardiopulmonary mortality and morbidity in the United States. Biodiesel is an alternative fuel from renewable feedstocks that can be immediately substituted in existing diesel engines. Considered by many to be a 'greener' alternative, U.S. biodiesel production reached record volumes of over 900 million gallons in 2011(25). Nevertheless, little is known about the impact of 'real world' biodiesel combustion on important particle characteristics (size, shape, surface area, number and composition) or about the relationship between human health and exposure to biodiesel PM (9,26). The unique collaboration established between the City of Keene, NH and Keene State College (KSC) over the past five years provides a robust infrastructure for undergraduate-based real world exposure studies. The City of Keene has been using biodiesel in their municipal fleet since 2002. Our preliminary and published work have led to the overarching hypothesis that replacing petrodiesel with biodiesel in nonroad engines will cause PM changes with direct relevance to human health. To address this critical issue, three specific aims are proposed, combining: (1) physical characterization of real world PM exposure profiles from nonroad engines, (2) chemical characterization of PM composition for known toxic/inflammatory compounds, and (3) biological characterization of the same PM to assess cellular responses and identify toxic/inflammatory components. Using an array of standard and novel environmental monitoring methods, KSC undergraduates will measure real world PM exposure profiles at a rural recycling site operating construction-type equipment. Equipment will first use commercial petroleum diesel fuel, and switch to a 20% biodiesel/80% petroleum diesel blend. PM samples will be chemically analyzed for toxic species of health concern including PAH's and metals. In a novel approach, the same field collected PM will be used by students for in vitro lung epithelial-cell assays to evaluate toxicological responses. The research outlined in this proposal will provide important information on the benefits and challenges associated with the real world use of biodiesel fuel as an intervention to reduce PM exposure risk from diesel engines, directly addressing NIEHS priorities in understanding the role of environmental exposure in human disease and translating research findings into prevention and intervention strategies to improve public health. This study provides a unique opportunity to engage KSC undergraduates from multiple departments in a cutting- edge, interdisciplinary investigation with direct implications for public health and environmental policy.